1. Field of the Invention
This invention relates to environmental seals and in particular to environmental seals for sealing transversely movable levers and the like across movement-accommodating openings.
2. Description of the Prior Art
In U.S. Letters Pat. No. 3,748,923 of John H. Babbitt, Jr. et al, owned by the assignee hereof, an improved seal assembly for sealing an opening about a transversely movable control element extending through the opening is disclosed. The seal assembly utilizes a stack of sealing plates which are overlapped to bridge the opening through which the control element extends. The plates may comprise spherically segmental plates and an elastomeric washer may be used to apply bias to the plates to reduce vibration.
A slot-closing device utilizing a similar relatively large plurality of sliding plates is shown in the earlier U.S. Letters Pat. No. 1,037,631 of John B. Jones.
The problem of sealing such control levers has become quite acute because of recent legislation which requires improved vehicle environmental operating conditions in connection with heavy duty earth moving equipment and the like. Thus, it is necessary to provide improved means for maintaining an environmental seal about control levers and the like extending through openings which are relatively large so as to accommodate substantial transverse movement of the control members in the operation of the apparatus. One earlier form of such environmental seal was an accordian-like rubber boot. Such boots, however, have the serious disadvantage of susceptibility to fatique and failure, and change in stiffness under different temperature conditions. Further, such boots tend to provide a biasing force on the control lever back to a centered position which, in most instances, is undesirable.